Bridging Perspectives: How Canadian Patients and Caregivers View Quality of Life in Multiple Myeloma Compared to Validated Instruments

<b>Background:</b> Validated patient- and caregiver-reported outcome (PRO and CRO) questionnaires are widely used to assess quality of life (QoL) in multiple myeloma (MM). However, most were developed before recent therapeutic advances that have modified disease trajectories and may no longer fully reflect patients' and caregivers' experiences. <b>Methods:</b> A Canadian cross-sectional observational study was conducted in collaboration with the PROxy Network and Myeloma Canada. Patients with MM completed the EORTC QLQ-C30, EORTC QLQ-MY20, EQ-5D-5L, and ESAS-R questionnaires and caregivers of patients with MM completed the CarGOQoL. Both groups rated their perceived QoL using a numerical rating scale. The strength of associations between validated questionnaire global scores and self-perceived QoL was assessed using Spearman's correlation coefficient (r). <b>Results:</b> Between October 2024 and February 2025, the study enrolled 305 patients and 104 caregivers. Moderate correlations were observed between patients' perceived QoL and validated PRO global scores (range of r: 0.59 to 0.65). The MM-specific QLQ-MY20 showed one of the lowest correlations (r = 0.59; 95% confidence interval (CI) 0.51-0.66; <i>p</i> < 0.001). The caregiver-reported CarGOQoL also demonstrated a moderate association (r = 0.54; 95% CI 0.38-0.67; <i>p</i> < 0.001). <b>Conclusions:</b> Contemporary treatment advances, including prolonged survival and evolving side effect profiles, may not be reflected in currently available PRO and CRO instruments.